This invention relates to telephone number information displaying devices in which, while the bell of a telephone set is ringing, the telephone number of a calling party is displayed at high speed.
A variety of techniques have been developed as means in which, while a called party is talking with a calling party after the latter dialed and the former picks us the handset the telephone exchange performs counter detection for the telephone number of the calling party upon the called party's request. Furthermore, there are some subscriber-owned systems in which the calling party's number can be transmitted to the called party side by the devices provided on both sides after the talk condition has been established.
However, these conventional devices are basically different in technical concept from this invention. Primarily, the invention has been developed for protecting privacy of a subscriber; that is, the invention has been developed for eliminating drawbacks inherent to the present telephone communication system. In the invention, while the bell of the telephone set is ringing, the dial information of the calling party is displayed at high speed (within one second). The Applicant has a Japanese Patent on this subject. However, it is in its early stage, and it is not so practical for other than use in a PBX (private branch exchange) in the present telephone exchange system as its dial information transmitting speed is very slow.
With respect to the above-described conventional device, a technique in which, when the user dials a telephone number, the telephone number is displayed on the device so that he may not make a mistake in dialing it, has been developed already. In the displaying device according to the invention, this effect is obtained by switching necessary or selected circuits with a greater part of the device maintained as it is. More specifically, the circuit for this purpose is so designed that if the user picks up the handset to dial, the necessary switching operation is automatically achieved.